Such a photon emitter is known from J. Kim et al., “A Single Photon-Turnstile Device, Letters to Nature,” Vol. 397, pages 500–503, February 1999.
In the case of this component known from J. Kim et al., it was described that individual photons with a frequency of 10 MHz can be emitted at an operating temperature of 50 mK. The photon emitter in accordance with J. Kim et al. is a component which has a mesoscopic double barrier pn heterojunction with a quantum film as active layer for emitting the photons. This photon emitter is based on the principle of a coulomb blockade for electrons and holes. The coulomb blockade prevents more than one electron from being able to tunnel into the active quantum film. In the photon emitter in accordance with J. Kim et al., the charge energy of a single electron must be greater than the thermal background energy. For this reason, the applicability of this known component is limited to very low temperatures in the range of mK.
It is known, furthermore, from J. M. Gerard and B. Gayral, “Strong Purcell Effect for InAs Quantum Boxes in a Three-Dimensional Solid-State Microcavity,” IEEE Journal of Lightwave Technology, Vol. 17, No. 11, pages 2089–2095, November 1999, that a quantum dot located in a semiconductor can be used in a resonator to generate single photons.
It is demonstrated experimentally in P. Michler et al., “A Quantum Dot Single-Photon Turnstile-Device,” Science, Vol. 290, pages 2282–2285, December 2000, that this is also possible in the case of non-resonant, optical pumping of the quantum dot, or in other words by exciting the quantum dot by optical pumping in the barrier.
It is to be pointed out in this connection that the excitation ground state of a quantum dot, which is produced by self-organized growth, can be predicted only within the inhomogeneous line width of the quantum-dot array. For this reason, the excitation ground state energy of a quantum dot and the energy of the resonator mode of a resonator correspond only randomly, and not in a fashion which can be predicted deterministically.
For this reason, the photon emitters in J. M. Gerard and B. Gayral, or P. Michler et al. are not suitable for application on a massive scale.
A vertical long-wave laser resonator with an integrated short-wave pumping laser is described in DE 199 47 853 A1 and EP 1 037 341 A2 in each case. The excited emission from the short-wave laser has the effect of activating the long-wave laser. An optically transparent adhesive fastens the lasers in vertical alignment.
Furthermore, a light-emitting semiconductor element with a quantum-dot region is disclosed in Patent Abstracts of Japan 10209572a or in A. Lott et al., “InAs—InGaAs quantum dot VCSELs on GaAs substrates emitting at 1.3 μm,” Electronics Letters, Vol. 36, No. 16, pages 1384–1385, August 2000.